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http://hdl.handle.net/20.500.12386/34350
Title: | Multiple stellar populations in the high-temperature regime: Potassium abundances in the globular cluster M 54 (NGC 6715) | Authors: | CARRETTA, Eugenio | Issue Date: | 2022 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 666 | First Page: | A177 | Abstract: | Among the multiple stellar populations in globular clusters (GCs) the very high-temperature H-burning regime, able to produce elements up to potassium, is still poorly explored. Here we present the first abundance analysis of K in 42 giants of NGC 6715 (M 54) with homogeneous abundances of light elements previously derived in our FLAMES survey. Owing to the large mass and low metallicity, a large excess of K could be expected in this GC, which is located in the nucleus of the Sagittarius dwarf galaxy. We actually found a spread in [K/Fe] spanning about 1 dex, with [K/Fe] presenting a significant anti-correlation with [O/Fe] ratios, regardless of the metallicity component in M 54. Evidence for a K–Mg anti-correlation also exists, but this is statistically marginal because of the lack of very Mg-poor stars in this GC. We found, however, a strong correlation between K and Ca. These observations clearly show that the K enhancement in M 54 is probably due to the same network of nuclear reactions generating the phenomenon of multiple stellar populations, at work in a regime of very high temperature. The comparison with recent results in ω Cen is hampered by an unexplained trend with the temperatures for K abundances from optical spectroscopy, and somewhat by a limited sample size for infrared APOGEE data. There are few doubts, however, that the two most massive GCs in the Milky Way host a K–Mg anti-correlation. | URI: | http://hdl.handle.net/20.500.12386/34350 | URL: | https://www.aanda.org/articles/aa/full_html/2022/10/aa44613-22/aa44613-22.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/202244613 | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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